[merged] fs-binfmt_elf-replace-open-coded-string-copy-with-get_task_comm.patch removed from -mm tree

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The patch titled
     Subject: fs/binfmt_elf: replace open-coded string copy with get_task_comm
has been removed from the -mm tree.  Its filename was
     fs-binfmt_elf-replace-open-coded-string-copy-with-get_task_comm.patch

This patch was dropped because it was merged into mainline or a subsystem tree

------------------------------------------------------
From: Yafang Shao <laoar.shao@xxxxxxxxx>
Subject: fs/binfmt_elf: replace open-coded string copy with get_task_comm

It is better to use get_task_comm() instead of the open coded string copy
as we do in other places.

struct elf_prpsinfo is used to dump the task information in userspace
coredump or kernel vmcore. Below is the verification of vmcore,

crash> ps
   PID    PPID  CPU       TASK        ST  %MEM     VSZ    RSS  COMM
      0      0   0  ffffffff9d21a940  RU   0.0       0      0  [swapper/0]
>     0      0   1  ffffa09e40f85e80  RU   0.0       0      0  [swapper/1]
>     0      0   2  ffffa09e40f81f80  RU   0.0       0      0  [swapper/2]
>     0      0   3  ffffa09e40f83f00  RU   0.0       0      0  [swapper/3]
>     0      0   4  ffffa09e40f80000  RU   0.0       0      0  [swapper/4]
>     0      0   5  ffffa09e40f89f80  RU   0.0       0      0  [swapper/5]
      0      0   6  ffffa09e40f8bf00  RU   0.0       0      0  [swapper/6]
>     0      0   7  ffffa09e40f88000  RU   0.0       0      0  [swapper/7]
>     0      0   8  ffffa09e40f8de80  RU   0.0       0      0  [swapper/8]
>     0      0   9  ffffa09e40f95e80  RU   0.0       0      0  [swapper/9]
>     0      0  10  ffffa09e40f91f80  RU   0.0       0      0  [swapper/10]
>     0      0  11  ffffa09e40f93f00  RU   0.0       0      0  [swapper/11]
>     0      0  12  ffffa09e40f90000  RU   0.0       0      0  [swapper/12]
>     0      0  13  ffffa09e40f9bf00  RU   0.0       0      0  [swapper/13]
>     0      0  14  ffffa09e40f98000  RU   0.0       0      0  [swapper/14]
>     0      0  15  ffffa09e40f9de80  RU   0.0       0      0  [swapper/15]

It works well as expected.

Some comments are added to explain why we use the hard-coded 16.

Link: https://lkml.kernel.org/r/20211120112738.45980-5-laoar.shao@xxxxxxxxx
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
Cc: Michal Miroslaw <mirq-linux@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/binfmt_elf.c                |    2 +-
 include/linux/elfcore-compat.h |    5 +++++
 include/linux/elfcore.h        |    5 +++++
 3 files changed, 11 insertions(+), 1 deletion(-)

--- a/fs/binfmt_elf.c~fs-binfmt_elf-replace-open-coded-string-copy-with-get_task_comm
+++ a/fs/binfmt_elf.c
@@ -1585,7 +1585,7 @@ static int fill_psinfo(struct elf_prpsin
 	SET_UID(psinfo->pr_uid, from_kuid_munged(cred->user_ns, cred->uid));
 	SET_GID(psinfo->pr_gid, from_kgid_munged(cred->user_ns, cred->gid));
 	rcu_read_unlock();
-	strncpy(psinfo->pr_fname, p->comm, sizeof(psinfo->pr_fname));
+	get_task_comm(psinfo->pr_fname, p);
 
 	return 0;
 }
--- a/include/linux/elfcore-compat.h~fs-binfmt_elf-replace-open-coded-string-copy-with-get_task_comm
+++ a/include/linux/elfcore-compat.h
@@ -43,6 +43,11 @@ struct compat_elf_prpsinfo
 	__compat_uid_t			pr_uid;
 	__compat_gid_t			pr_gid;
 	compat_pid_t			pr_pid, pr_ppid, pr_pgrp, pr_sid;
+	/*
+	 * The hard-coded 16 is derived from TASK_COMM_LEN, but it can't be
+	 * changed as it is exposed to userspace. We'd better make it hard-coded
+	 * here.
+	 */
 	char				pr_fname[16];
 	char				pr_psargs[ELF_PRARGSZ];
 };
--- a/include/linux/elfcore.h~fs-binfmt_elf-replace-open-coded-string-copy-with-get_task_comm
+++ a/include/linux/elfcore.h
@@ -65,6 +65,11 @@ struct elf_prpsinfo
 	__kernel_gid_t	pr_gid;
 	pid_t	pr_pid, pr_ppid, pr_pgrp, pr_sid;
 	/* Lots missing */
+	/*
+	 * The hard-coded 16 is derived from TASK_COMM_LEN, but it can't be
+	 * changed as it is exposed to userspace. We'd better make it hard-coded
+	 * here.
+	 */
 	char	pr_fname[16];	/* filename of executable */
 	char	pr_psargs[ELF_PRARGSZ];	/* initial part of arg list */
 };
_

Patches currently in -mm which might be from laoar.shao@xxxxxxxxx are





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